Our story begins with the Phantom Legion, a gang of armored (and, oddly enough, cat-tailed) villains, creating a huge explosion. Later, they gather in front of a vidscreen to receive the praise of their faceless master for bringing him the pleasure of human screams. Singled out for praise is the leader of the strike force, Volken, an armored devil in a trench-coat. The Legion is encouraged to keep up the good (aggressively destructive) work.

The next morning, perfectly ordinary high-school student Toichi Tenkawa listens quietly as his fellow students discuss the explosion, wondering if it was once again the work of the Phantom Legion. Foolish humans, he thinks, how terrified they’d be to discover that the Phantom Volken has taken human form and lives among them.

Lost in thought, he’s surprised when the other boys go wild at the sight of their new transfer student, Kokoro Maishima, a busty blonde who’s also loud, rude, and not the least bit interested in these pathetic boys. Naturally, she’s assigned to the empty seat next to Toichi. Despite her outburst, he politely greets his new classmate and offers to help her out if there’s anything she doesn’t understand. She rebuffs him with a blunt “omae, urusai zo”, shocking and angering him.

Later, Volken and his Phantoms lie in wait to begin their latest act of evil, hijacking a pre-school bus. As they move into position, they’re interrupted by a mysterious and quite curvy figure: The Angel of Judgement, Mighty Heart. Volken/Toichi is stunned to recognize his new classmate, and even more surprised as she leaps into the fray, and is instantly defeated by his minions.

Tied up, Our Heroine’s feminine charms are well-displayed in her skimpy costume, and one of the minions politely suggests a way to deal with their prisoner: they want her to join the gang. Surprised, Volken demands an explanation, and he explains that having a girl around would “enhance” their all-guy family. Volken nixes the plan, so the outspoken minion settles for a little fun, groping his way toward her breasts and commenting on how soft they’ll feel, and if she were to join the gang, she’d be vigorously groped like this all the time.

Our heroine is distressed, and to his surprise, Volken is also distressed, and moves to intervene, ordering them to act like professionals. Unfortunately, he trips on a rock, and catches himself with both hands on her ample breasts. The minions cheer (“Sasuga Volken-sama!”), but Volken is embarrassed, and tries to reassure the crying prisoner that it was an accident, and he was just trying to stop them from molesting her.

Too late. With a mighty explosion, Volken and his minions are defeated, and our sobbing heroine walks off into the sunset. Her true strength, it seems, is buried deep, and only moments of extreme shyness can allow her to call forth her Mighty Beam.

(end chapter one)

Coming from Shonen Champion Comics (publishers of Puri Puri, Zokusei, Hanaukyou Maid Tai, Mai-HiME, and Penguin Musume, among others), I expected Mighty Heart to live up to the “chotto ecchi” part of the back-cover blurb “chotto ecchi-na dokidoki kindan love comedy”. Certainly the cover art suggested as much:

And the back cover added fuel to the fire:

Pantsu everywhere, of course. Naughty tentacles make their first appearance in chapter two, as MH tries to rescue some other girls from a Phantom octopus monster that’s hiding in the school pool. Watching from a distance, Volken feels compelled to help her, and throws his sword, severing the tentacles, and somehow managing to accidentally slice open her top. When she sees her breasts bared, her shyness once again triggers her Mighty Beam, destroying the monster. She saves the sword, a precious item from an unknown helper.

In chapter three, Volken is given a slight demotion for his interference, and introduced to his new captain, the boss’s barely-clad daughter, Karol. As soon as daddy’s off the screen, she glomps him, reminding him of her childhood promise to be his lover someday. He’s saved by a scramble alert: MH has been sighted, and Karol is eager to show Volken how it’s done, first defeating her between panels, and then pinning her down for three pages of hot girl-on-girl tongue kissing.

Volken sees the warning signs and tells Karol to run, as MH gets to her feet and shouts that she’ll never forgive Karol for stealing her first kiss. He throws a few smoke bombs as a distraction, briefly crosses (identical!) blades with her, then scoops up Karol and runs like hell, only getting bruised in the resulting Mighty Beam explosion.

Back in his Toichi disguise, he limps hack to his lonely apartment, where he finds Karol (“okaeri, onii-chan”) has moved in with him, taking full advantage of her new position as his superior officer.

In chapter four, Toichi takes out the recyclables, while nearby, classmate Kokoro plays innocently with a neighborhood dog. Well, innocent until the dog manages to knock her to the ground and mount her from behind. Naturally, Toichi shows up just in time to see this. Later, some punks have tied up the dog and are tormenting it with fireworks. Volken scares them off, only to be confronted by MH, who’s convinced that he’s the villain.

Well, he is a villain, but naturally he’s upset that she thinks he’d stoop to something like this. She scolds him as she unties the dog, which promptly dives up her skirt for a sniff, and then tears off her panties. Uh-oh; Volken grabs the dog, tries to calm her down, and then it’s Mighty Beam time. At school the next day, a severely disgruntled Toichi finds himself being bullied by the same punks, and is on the verge of using his powers against them when Kokoro intervenes, tells them off, and then tells Toichi let her know if anyone bothers him again.

She walks off with a sweet smile, and his heart thumps. Uh-oh.

It gets sillier after that, and that’s only part of volume 1. In chapter 18, Kokoro is taking the trash out after school, and finds a curious mushroom by the dumpster. It’s a kind she’s never seen before, and as she touches it, it explodes with spores. Little does she know that one of those spores has found a dark, moist place to grow.

She finds out when the other girls run screaming away from her in the locker room, pointing at the suspicious bulge in her skirt. She tries to sneak out of the school, only to be called to duty as MH. She confronts the Phantom minions with her hands firmly holding down her skirt, until Karol shows up, and the mushroom springs to life.

Everyone is surprised, but MH decides this was Karol’s work, and attacks, pinning her down, the rampant mushroom making the scene quite, um, “suggestive”. Naturally, a stunned Volken shows up in time for combat interruptus, and an embarrassed MH flees the scene while Karol cries on his shoulder. In the background, one minion asks another what will happen to the mushroom, and is told that it will fall off on its own in 24 hours.

Three volumes out so far (1, 2, 3, and yes, that’s Karol on the cover of 2), a text-only Japanese Wikipedia entry, and the mangaka’s official blog (which has occasional pictures, including a less-censored version of one scene from volume one).

Here’s one from the blog: